System for minimizing static



I Jan. 13, 1 931. c. w. WQODRQFF 1,789,208

SYSTEM FOR MINIMIZING STATIC Fild Jan. 31, 1928 zlwucmtoc CHARLES W. WOODRUFF Patented Jan. 13, 1931 I omen.STATES PATIENT OFFICE CHARLES w. woonn'orr, or contrmnus, OHIO. 7

SYSTEM non innmizme STATIC Application filed January 31, 1928. Serial No, 250,840.

My invention relates to. asystem for minimizing the effect of staticupon radio receiving devices. 7

-The efiects of static or atmospheric electricity is usually manifested in radio receiving apparatus by noises varying from hlssing sounds to sharp crashes. The hissing and; frying sounds usually have a normal volume which may be termed the normal static level,

6 and the crashes are interspersed at various and indeterminate intervals depending upon atmospheric and, other conditions.

I object. of my invention is to devise a system for reducing the effect of atmospheric 3 electricity upon the reception of radio signals,

and in particulanto devise an arrangement in which the effect of the normal static level is rendered imperceptible and also the efiecti of the static crashes is reduced to an unobjeco tionable volume.

;A further object of my invention,is' to de v vise a system for reducing the, effects of static upon'radio reception without a substantial reduction rinothe volume of signal re- 1 My inventionis illustrated in the accompanying drawing which is a schematic diagram of-P'the circuit arrangement employed. '1

--In the drawing, AN indicates an antenna for snpplyingireceived energy to a radio receiving set S of usualconstruction employing vacuumtube relays and having a loud speaker LS connected -thereto. The antenna AN is connected to one plate element P of a double-waverectifier tube RT. The

filament F- of the rectifier tube RT is energized from the A battery of the radio set RS as shown. The second plate element P is connectedto the antenna terminal a of the I 49 radio set and the ground terminal I; is

grounded at GN in the usual manner. The

A battery is grounded in the usual manner through the ground terminal as indicated in dotted line. The antenna AN is also con-' 423 nected tothe variable arm of a three-point tap switch TS. The contact 10f tap switch TS is connected to the variable arm off static minimizer cell M. The contact 2 is connected to one terminal of a variable resistanceR,

-50 and contact 3 is connected to one terminal of a Variable condenser Theremaining terminals of the elements M, R and G are joined together and connected to the antenna I terminal aof the set BS. The minimizer M 1s constructed. in accordance with the dis-V closure n my copending application Ser. No.

6,813, filed September 4, 1925. It consists' of a number ofelectrolytic cells connected in series, each cell comprising a container filled with electrolyte and provided withsuitable electrodes. For example, the electrolyte may be a solution of ammonia phosphate and the electrodes may be lead and aluminumor both'of'aluminum." Connections are made I from between each cell to points on a tap switch in order that the number of cells insystem maybe obtained with the arm of tap switch TS placed in a position out of contact with any of its contact points. In this condition the operation is'believed to be as fol- I lows: The incoming current supplied by the antenna is impressed upon the plate P of the rectifier tube RT and the positive alternations ofthe wave as well as'the positive po'r-,

'tions' ofthe static'i'nterferen'ce are conducted to ground by Wayoftherectifier path between the filament F and the plate P that'is thispath' serves to conduct at least a portion of the energy of the positive portions of the wave to. ground. Undoubtedly the natural P and P ,*which is indicated at C is'eifectiv'e'in transfering'or afiording a path for the high frequency current from-the antenna 1 to the antenna terminal a of the receiving set. The filament F and the plate P also con-- capacity existing between the plate elements stitute a rectifying element connected between the antenna terminal ofthe set and the ground, and functionsin a mann'er siini' 'lar to the rectifying element-referred to above. It is'obvious that the negative alternations are not conducted toground through either of the rectifying elements. I do not reception.

minimizer and the ground. It is believed While I have efiect of the static is satisfactorily reduced somewhat at the expense'of the volume of and the antenna terminal of the set, as by means of the taplswltch TS. The 1111111- mizerlt'i is effective not onlyin reducing the effect of. static upon the reception, in addition to theoperation of the rectifier tube RI but itserves tomcrease the volume of reception. The action ofthese two elements appears to be com lemental that is one element a ears- P a U to be operatlve to reduce'tne'enectsof static ground, and the filament in combination with plate P constitute a second rectifier pathconnected vbetween the other terminalof that the first rectifier path is effective in reducmg both the normal stat c level and the static crashes to a minimum and the second rectifier path serves to effectively reduce such amounts of static as are transmitted through the minimizer M. The action of the cell is such that large impulses or crashes above a predetermined intensity causes a marked increase in the resistance of the cell practically simultaneously with the impulses, while only a small increase of resistance is caused by signals below this intensity.

I- find that satisfactory operation with increased volumemay also be obtained by substituting for the minimizer M a variable'resistance'R, or a variable condenser G. This may be done by changing the position of the arm of tap switch TS to include the desired element in the circuit. 1

It is obvious that instead of incorporating both rectifier paths into a single tube element,

separate two-element tubes may be employed for each path. 7 I l shown one form of my invention for the purpose of explanation, it is obvious that the details may be varied without departing from-the essence of the invention.

WhatIclaim is: I 1. In combination, an antenna, a radiofreceiving. set provided with antenna and ground terminals, a. double plate thermionic I find that the volume may be brought up to a satisfactory value by connecting the minimizer M between the antenna ode, said antenna being connected to one plate of the rectifier and the other plate being connected to the antenna terminal of the receiving set, and a path from thecathode of the rectifier to ground. a i

2. In combinatioman antenna, a radio re ceiving set provided with antenna and.

ground terminals and an energizing battery connected to said ground terminal, a rectifier tube compr slnga filament and two plate elements cooperating therewith, a circuitforenergizing the filament fr'omthe said battery," said antenna being connected to one plate element, and the other plate element being connected to the antenna terminal ofthe receiving set. t

a 3. In combination,'an antenna, a radio receiving set provided with antenna and ground terminals, adouble-plate thermionic rectifier including an electron emitting cathode, said antenna being connected to one plate of the rectifier and the other plate being connected to the antenna terminal of the receiving set, an impedance element connected between the two plateelements'of the rectifier, and a path from the cathode of the rectifier to ground. a

4. In combination, an antenna, a radio receiving set provided with thermionicprelays and antenna and ground terminals, an energizing battery'for said relays connect-' ed to. ground through said ground termi-.

had, a rectifier tube comprising a filament and two plate elements cooperating there-r with, a circuit for energizing 111118 filament from the said battery, said antenna being connected to one plate element, and the other plate element-being connected to. the antenna. terminal of the receivingset.

5. In combination, anantenna, a. radio receiving set provided 'with antenna and groundterminals', a double-plate thermionic rectifier: includingan electron emitting cathode,""said' antenna being'gconnected to one plate of the rectifier and the other plate be; ing connected to theantenna terminal of the receiving set, a static, reducing element connected between the two plate elements of ,therectifier, and a path from the cathode ofthe'rectifier to ground.

6.:In combination, an antenna, a radio receiving set provided with thermionic re lays and antennajand aground terminals, an energizing battery for said relays connected to ground; through said groundjterminal, a

rectifiertubecomprising a filament and two plate elementscooperatingtherewith, a circuitqfor energizing-the filament from the sa-idbattery, said antenna being connected to oneplate element, the other plate element being connected tothe antenna terminal. of the receiving set, and an impedance element connected between said plate elements. 77:.In combmatlon, an antenna, a radio recelvingiset, .an-antenna circult extending from the antenna to ground and including the receiving set and an impedance element between the antenna and the set, an asymmetrically conducting path connected between the antenna and ground, and a second asymmetrically conducting path connected between the input terminal of the set and ground.

8. In combination, an antenna, a radio receiving set, an antenna circuit including the recelvlng set and a static reducing element connected in said circuit between the antenna and the set, and an asymmetrically conducting path connected from one terminal of said element to ground.

9. In combination, an'antenna, a radio receiving set, an antenna circuit extending from the antenna to the ground through said receiving set, an electrolytic cell connected in said circuit between the antenna and the receiving set, and an asymmetrically conducting path connected between the antenna and ground.

a 10. In combination, an antenna, a radio receiving set, an antenna circuit extending from the antenna to the ground through said receiving set, a resistance connected in said circuit between the antenna and the receiving set, and an asymmetrically conducting path connected between the antenna and ground, and a second'asymmetrically conducting path connected between the antenna terminal of the set and ground.

11-. In combination, an antenna, a radio receiving set, an antenna circuit extending from the antenna to the ground through said receiving set, a condenser connected in said circuit between the antenna and the receiving set, and an asymmetrically conducting path connected between the antenna and ground, and a second asymmetrically conducting path connected between the antenna terminal of the set and ground.

In testimony whereof I have hereunto signed my name.

CHARLES W. WOODRUFF. 

